Polygon at the Verge has an editorial based on a presentation that Chris Avellone did at GDC Online Panel. In it, he talks about how Obsidian "expanded the Fallout: New Vegas universe with 10,000 lines of dialogue". As always, a snip:

The studio had to streamline the voice-over recording process as much as possible to stay under budget. That process involved sending casting directors extensive rundowns on specific characteristics Obsidian desired for each voice actor. They then worked with the actors to give as much background on the characters in as little a time as possible, and passed along a script that had been annotated to provide important context to dialogue — things like intended tone and pronunciations of esoteric terms were bracketed, and placed in the script.